This invention relates to a synchronized dog clutch applicable to inboard-outboard stern drive marine propulsion units or other power transmission mechanisms, and particularly to synchronized dog clutches wherein power is transmitted between a gear wheel and a clutch shaft by a coupling sleeve and a synchronizer ring.
Conventionally, a clutch of the type mentioned above comprises, as shown in FIG. 1 a clutch shaft 1 (input shaft or output shaft), a cylindrical synchronizer ring 2 splined to the shaft 1, and a coupling sleeve 3 splined to the outer periphery of the ring 2. The synchronizer ring 2 is provided with a conical face 5 for frictional engagement at an outer periphery of its end. The coupling sleeve 3 is provided with claws 6 at the end. A bevel gear wheel 7 is coaxially and rotatably arranged around the clutch shaft 1, and is provided with claws 8 and a conical face 10. The claws 8 are meshable with the claws 6, and the face 10 is frictionally engagable with the face 5.
In the engagement operation the coupling sleeve 3 is shifted toward the gear wheel 7 by a shift mechanism (not shown). Initially the synchronizer ring 2 is shifted together with the coupling sleeve 3 by a detent mechanism 11, and the conical face 5 is first pressed against the conical face 10, whereby the rotation of the shaft 1, the ring 2 and the sleeve 3 is sychronized with that of the gear wheel 7. After the synchronization, the detent mechanism 11 yields, the sleeve 3 is further shifted on the ring 2, and both claws 6 and 8 are meshed with each other. When they are meshed, since the rotation of the claws 6 and 8 is synchronized, shock is not generated. However in the clutch stated above, since the conical face 10 is formed at the inner portion of the gear wheel 7, the effective radius of the face 10 is short. Therefore, in order to transmit sufficient torque through the face 10 for synchronization, it is necessary to employ the big gear wheel 7 and the ring 2, and also to employ the detent mechanism 11 having a strong detent force (corresponding to the pressure force between the faces 5 and 10), which increases the size and cost of the clutch, and also increases the force required for clutch operation. Further, in the above-stated clutch, the following disadvantage may result. Namely, if the friction force between the sleeve 3 and the ring 2 is larger than that between the ring 2 and the shaft 1, since the sleeve 3 may return to the neutral position without sliding on the ring 2 in the release operation, the ring 2 is fixedly held and returned by the sleeve 3 to a position which is remote from the neutral position in the opposite direction to the gear wheel 7, whereby the intended operation of the ring 2 is not obtained in the next engagement operation. In other words, both claws 6 and 8 are meshed with each other before the face 5 touches the face 10 in the next operation, and thereby the undesired shock is generated.
Accordingly, it is an object of the invention to provide an improved synchronized dog clutch, wherein a gear wheel having teeth at its outer periphery is provided both with a conical face for frictional engagement lying closely and radially inside the outer teeth, and with claws lying radially inside the conical face, whereby the effective radius of the conical face is increased, the torque for synchronization is increased, and thereby a compact and easily operated clutch is obtained.
Another object of the invention is to provide an improved mechanism for obtaining an exact shift of a synchronizer ring and a coupling sleeve relative to each other without fail.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.